A number of medical procedures involve or can be supplemented with the placement of an endoluminal prosthesis, commonly referred to as a stent, that can be implanted in a lumen, such as a blood vessel or other natural pathway of a patient's body. Such stents typically define a generally tubular configuration, and are expandable from a relatively small diameter (low profile) to an enlarged diameter. While in its low profile configuration, the stent is advanced endoluminally, by a delivery device, through the body lumen to the site where the stent is to be placed. The stent then can be expanded to a larger diameter in which it can firmly engage the inner wall of the body lumen. The delivery device then is removed, leaving the implanted stent in place. In that manner, the stent may serve to maintain open a blood vessel or other natural duct, the functioning of which had become impaired as a result of a pathological or traumatic occurrence.
Among the medical procedures in which stents have had increasing use is in connection with percutaneous transluminal angioplasty (PTA), and particularly percutaneous transluminal coronary angioplasty (PTCA). PTA and PTCA involve the insertion and manipulation of a dilating catheter through the patient's arteries to place the dilatation balloon of the catheter within an obstructed portion (stenosis) of a blood vessel. The balloon then is expanded forcibly within the obstruction to dilate that portion of the blood vessel thereby to restore blood flow through the blood vessel. Among the more significant complications that may result from such angioplasty is that in a significant number of cases, the dilated site again becomes obstructed. By placing a stent within the blood vessel at the treated site, the tendency for such restenosis may be reduced.
Stenoses often may develop in the branching region of a patient's blood vessel. Treatment of a stenosis in the branched region may present numerous additional difficulties in the design of devices to dilate stenoses at the branched region.
A number of stents have been proposed and developed in the art, including single stents that define a single luminal pathway as well as bifurcated stents that define a branched pathway and are intended to be placed in a branching region of a blood vessel. The development of bifurcated stents, as compared to single stents, presents numerous difficulties because of the branched arrangement and the difficulty in delivering and placing a bifurcated stent at the branched region of a blood vessel.
In one arrangement, disclosed International Application No. PCT/IB96/00569, filed Jun. 7, 1996, entitled "Bifurcated Endovascular Stent" a bifurcated stent is formed from two, initially independent, component stents. In the preferred embodiment each component stent is formed from wire and has an elongate spine and a plurality of generally tube-defining modules connected to the spine in a longitudinally sequenced array. Each component stent defines a generally tubular configuration. The modules on the two component stents are arranged to enable them to be combined, in situ, to form a bifurcate configuration. Each component stent may be considered to have a proximal set of modules and a distal set of modules. The modules in the proximal set of one component stent are arranged longitudinally to enable them to be interfitted with a complementary module set on the proximal end of the other component stent.
The device is placed at the vessel bifurcation by first inserting one of the component stents to place its proximal module set in the common blood vessel and its distal module set in one of the branches of the blood vessel. The first placed component stent is provided with a side opening between its ends and is placed so that the side opening is positioned at the juncture of the blood vessels to provide access to the branch vessel. The modules in the first component stent then are expanded to secure the first component stent in place. The second component stent then can be advanced into and through the first component stent and transversely through the side opening of the first stent to project the distal module set of the second component stent into the second branch of the blood vessel. With the second component stent so placed, and with its proximal module set aligned to fit in complementary fashion with the proximal module set of the first component stent, the second component stent can be expanded in place.
The present invention is directed to an improved method and apparatus for placing the component stents in a bifurcated configuration in a branched vessel. A further object of the invention is to provide improvements in stent construction by which the stent can provide substantially continuous support for the vessel, including the region of the vessel junction.